
/* Copyright 1998 by the Massachusetts Institute of Technology.
 * Copyright (C) 2009 by Jakub Hrozek <jhrozek@redhat.com>
 *
 * Permission to use, copy, modify, and distribute this
 * software and its documentation for any purpose and without
 * fee is hereby granted, provided that the above copyright
 * notice appear in all copies and that both that copyright
 * notice and this permission notice appear in supporting
 * documentation, and that the name of M.I.T. not be used in
 * advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.
 * M.I.T. makes no representations about the suitability of
 * this software for any purpose.  It is provided "as is"
 * without express or implied warranty.
 */

#include "ares_setup.h"

#ifdef HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#ifdef HAVE_NETDB_H
#include <netdb.h>
#endif
#ifdef HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif
#ifdef HAVE_ARPA_NAMESER_H
#include <arpa/nameser.h>
#else
#include "nameser.h"
#endif
#ifdef HAVE_ARPA_NAMESER_COMPAT_H
#include <arpa/nameser_compat.h>
#endif

#ifdef HAVE_STRINGS_H
#include <strings.h>
#endif

#include "ares.h"
#include "ares_dns.h"
#include "ares_data.h"
#include "ares_private.h"

static int
ares__parse_txt_reply(const unsigned char* abuf, int alen,
    int ex, void** txt_out)
{
    size_t substr_len;
    unsigned int qdcount, ancount, i;
    const unsigned char* aptr;
    const unsigned char* strptr;
    int status, rr_type, rr_class, rr_len;
    long len;
    char *hostname = NULL, *rr_name = NULL;
    struct ares_txt_ext* txt_head = NULL;
    struct ares_txt_ext* txt_last = NULL;
    struct ares_txt_ext* txt_curr;

    /* Set *txt_out to NULL for all failure cases. */
    *txt_out = NULL;

    /* Give up if abuf doesn't have room for a header. */
    if (alen < HFIXEDSZ)
        return ARES_EBADRESP;

    /* Fetch the question and answer count from the header. */
    qdcount = DNS_HEADER_QDCOUNT(abuf);
    ancount = DNS_HEADER_ANCOUNT(abuf);
    if (qdcount != 1)
        return ARES_EBADRESP;
    if (ancount == 0)
        return ARES_ENODATA;

    /* Expand the name from the question, and skip past the question. */
    aptr = abuf + HFIXEDSZ;
    status = ares_expand_name(aptr, abuf, alen, &hostname, &len);
    if (status != ARES_SUCCESS)
        return status;

    if (aptr + len + QFIXEDSZ > abuf + alen) {
        ares_free(hostname);
        return ARES_EBADRESP;
    }
    aptr += len + QFIXEDSZ;

    /* Examine each answer resource record (RR) in turn. */
    for (i = 0; i < ancount; i++) {
        /* Decode the RR up to the data field. */
        status = ares_expand_name(aptr, abuf, alen, &rr_name, &len);
        if (status != ARES_SUCCESS) {
            break;
        }
        aptr += len;
        if (aptr + RRFIXEDSZ > abuf + alen) {
            status = ARES_EBADRESP;
            break;
        }
        rr_type = DNS_RR_TYPE(aptr);
        rr_class = DNS_RR_CLASS(aptr);
        rr_len = DNS_RR_LEN(aptr);
        aptr += RRFIXEDSZ;
        if (aptr + rr_len > abuf + alen) {
            status = ARES_EBADRESP;
            break;
        }

        /* Check if we are really looking at a TXT record */
        if (rr_class == C_IN && rr_type == T_TXT) {
            /*
           * There may be multiple substrings in a single TXT record. Each
           * substring may be up to 255 characters in length, with a
           * "length byte" indicating the size of the substring payload.
           * RDATA contains both the length-bytes and payloads of all
           * substrings contained therein.
           */

            strptr = aptr;
            while (strptr < (aptr + rr_len)) {
                substr_len = (unsigned char)*strptr;
                if (strptr + substr_len + 1 > aptr + rr_len) {
                    status = ARES_EBADRESP;
                    break;
                }

                /* Allocate storage for this TXT answer appending it to the list */
                txt_curr = ares_malloc_data(ex ? ARES_DATATYPE_TXT_EXT : ARES_DATATYPE_TXT_REPLY);
                if (!txt_curr) {
                    status = ARES_ENOMEM;
                    break;
                }
                if (txt_last) {
                    txt_last->next = txt_curr;
                } else {
                    txt_head = txt_curr;
                }
                txt_last = txt_curr;

                if (ex)
                    txt_curr->record_start = (strptr == aptr);
                txt_curr->length = substr_len;
                txt_curr->txt = ares_malloc(substr_len + 1 /* Including null byte */);
                if (txt_curr->txt == NULL) {
                    status = ARES_ENOMEM;
                    break;
                }

                ++strptr;
                memcpy((char*)txt_curr->txt, strptr, substr_len);

                /* Make sure we NULL-terminate */
                txt_curr->txt[substr_len] = 0;

                strptr += substr_len;
            }
        }

        /* Propagate any failures */
        if (status != ARES_SUCCESS) {
            break;
        }

        /* Don't lose memory in the next iteration */
        ares_free(rr_name);
        rr_name = NULL;

        /* Move on to the next record */
        aptr += rr_len;
    }

    if (hostname)
        ares_free(hostname);
    if (rr_name)
        ares_free(rr_name);

    /* clean up on error */
    if (status != ARES_SUCCESS) {
        if (txt_head)
            ares_free_data(txt_head);
        return status;
    }

    /* everything looks fine, return the data */
    *txt_out = txt_head;

    return ARES_SUCCESS;
}

int ares_parse_txt_reply(const unsigned char* abuf, int alen,
    struct ares_txt_reply** txt_out)
{
    return ares__parse_txt_reply(abuf, alen, 0, (void**)txt_out);
}

int ares_parse_txt_reply_ext(const unsigned char* abuf, int alen,
    struct ares_txt_ext** txt_out)
{
    return ares__parse_txt_reply(abuf, alen, 1, (void**)txt_out);
}
